A dual stage positioning and switching system is used for the switch of two wafer stages. The wafer stages cooperate with the base, X-direction guide bars, Y-direction guide bars, motion positioning detectors, linear gratings, etc. to complete the switching process. The above system can be used in the field of lithography machine manufacturing.
A lithography machine, which exposes and transfers the design pattern of a chip onto the photoresist coated on a wafer, is one of the important devices used in IC chip manufacturing. A main part of a lithography machine is the wafer stage positioning and switching system, whose operation accuracy and running speed greatly influences the throughput of a lithography machine.
A complete exposure process comprises such sub-processes as wafer loading, pre-alignment, alignment, level adjustment detection, exposure, wafer unloading, etc. In a dual stage structure, the wafer stage of the pre-processing workstation carries out wafer loading/unloading, pre-alignment, alignment, level adjustment detection and other pre-processing steps, while the wafer stage of the exposure workstation carries out the exposure steps. The two workstations operate simultaneously to shorten the cycle of the exposure process of a wafer, and thereby improving the throughput of the lithography machine.
Referring to FIG. 1, a lithography machine adopting dual stage structure comprises from the top down an illumination system 17, a reticle stage positioning system 16, a projection object lens system 15, a focus and level adjustment detecting system 14, an alignment system 13, a first wafer stage positioning unit 2a for the pre-processing workstation, a second wafer stage positioning unit 2b for the exposure workstation, and a base 1.
Present dual stage structures can achieve the positioning and switching of two wafer stages, but there remain some disadvantages of the present structures: since a wafer stage has a lot of cables connected thereto, such as the gas supplying pipelines, the control lines for adjusting the vertical (Z-direction) positions of the wafer stages, cables of the sensors for detecting the X and Y direction positions of the wafer stages and other sensor circuits, cables of the circuit that controls the loading and unloading of the wafer, etc. A cable stage is needed to collect all the above cables, and it must be controlled to move synchronously with the wafer stage. The operation of the cable stage directly influences the motion positioning accuracy and the dynamic performance of the wafer stage, thus increasing the cost of the dual stage structure as well as the difficulty in the positioning and switching of the two stages. Moreover, during the synchronous operations of the two stages, due to the overlapped work space, the stages are likely to interfere with each other, and the paths of the stages may also overlap. Therefore, devices for preventing collision between the stages are needed, so that the manufacturing cost is raised.